Prior art methods for use in making forms of the type used in casting concrete have employed the use of expanded polystyrene foam slabs or blocks with a decorative configuration cut into the surface of the foam slab. During the casting of the concrete, the decorative configuration will be formed in the surface of the cast concrete. The prior art apparatus for use in forming such decorative configurations has included machines having an elongated heated electrically conductive wire and means for pulling this wire through a block of polystyrene foam to form a patterned or contoured surface in the foam. The heated wires may also be bent so as to cut a contoured surface pattern as the wire is moved through the foam block. The contoured surface is formed by moving the bent wire in three dimensions and by controlling the rate of movement of the wire through the block. Such an apparatus is illustrated in a brochure titled "Concrete Renaissance Through Building Technology". 1982, Down To Earth Bookshop Press, Perth, W. Australia, pages IX-X.
Attention is also directed to the Ritter U.S. Pat. No. 3,965,233, issued June 22, 1976. That patent relates to a method for producing a cast concrete article employing an expanded polystyrene foam form liner having a face which is textured or patterned to produce a complementary pattern in the surface of the molded product. The Ritter patent suggests the formation of a contoured surface on the face of the foam portion of the mold using electrically heated printing tools. The printing tools include an electrical element fixed to a frame or handle, and this electrical element is shaped so as to form a geometric impression on the foam. The patent also teaches a printing tool comprising an elongated support member supporting a wire forming a plurality of U-shaped loops. The loops are moved along the face of the form to produce a grooved pattern.